1. Field of the Invention
The present invention relates to a lighting device and more particularly to a vehicle headlamp which includes a reflector for reflecting a light emitted from a light source.
2. Related Art
There is a lighting device for a vehicle using a semiconductor light emitting device such as an LED (Light Emitting Diode). JP-A-2008-226707 discloses a lighting device for a vehicle in which a light emitted from each of LEDs is reflected by a reflector so as to form a light distribution pattern for a hot zone and a light distribution pattern for a diffusion region.
In order to enhance a distance visibility, it is important to increase a luminous intensity in a vicinity of an upper cut-off line in a light distribution pattern for a low beam, thereby causing the cut-off line to be clear. Some reflectors have a plurality of reflecting surfaces and synthesize lights (projection images) reflected by respective reflecting surfaces, thereby forming a light distribution pattern for a low beam which has the cut-off line.
Depending on a design of a vehicle, however, a shape of a lighting device for a vehicle is restricted. For example, it is considered, in a lighting device for a vehicle, to take away a part of a reflector. Each reflecting surface of the reflector forms a part of a light distribution pattern for a low beam. Therefore, it is hard to form a desirable light distribution pattern if a part of reflecting surfaces is decreased. If reflecting surfaces for forming a cut-off line of the light distribution pattern for a low beam are decreased, particularly, it is difficult to form a clear cut-off line.